Jan. 31, 2012 -- An experimental pill that works differently than other
prostate cancer drugs extended the lives of men with spreading cancer by an average of nearly five months.

Men with late-stage prostate cancer given the new hormone treatment, MDV3100, lived an average of nearly a year-and-a-half from the time they started taking the treatment, compared with fewer than 14 months for those given placebo.

MDV3100 works differently than other hormone treatments, launching a three-pronged attack against testosterone and its related hormones, called androgens, which fuel prostate cancer growth.

All the men had cancers that continued to spread despite previous hormonal therapy and chemotherapy.

"About 32,000 men die of prostate cancer each year in the U.S., and virtually all the deaths are due to this type of cancer," says Howard I. Scher, MD, chief of the genitourinary oncology service at Memorial Sloan-Kettering Cancer Center in New York.

Researchers not involved with the study were impressed by the results.

Scher presented the findings at a news briefing in advance of the fourth annual Genitourinary Cancers Symposium, being held later this week in San Francisco. He is an unpaid consultant for Medivation, which makes the drug and funded the trial.

The survival edge was so substantial that the late-stage study was halted early so men taking placebo could be offered MDV3100. Results of the study are being submitted to the FDA in anticipation of gaining approval, Scher tells WebMD.

If approved, MDV3100 would join a growing number of drugs for late-stage disease. Most recently, the prostate cancer pill Zytiga got the nod from the FDA after a large study showed it may extend life by up to four months.

"The major difference is that Zytiga requires that men also receive prednisone, which produces side effects like fluid retention that have to be managed. MDV3100 does not," Scher says.

Drug Well-Tolerated

In the study, called AFFIRM, almost 1,200 men were given MDV3100 or a placebo.

In addition to living longer, men who took the new pill were more likely to experience drops in levels of prostate-specific antigen (PSA) than men who received placebo. Elevated levels of PSA may be an indicator for prostate cancer.

The men who took MDV3100 also showed improvements in disease-related symptoms and prostate cancer progression on imaging tests compared with men who received the placebo.

Importantly, MDV3100 was well-tolerated, Scher says. In fact, men taking placebo were slightly more likely to experience serious side effects. The most common side events occurring more frequently in the MDV3100 group were mild fatigue, diarrhea, and hot flushes.

"This is an outstanding drug," says Bruce Roth, MD, a prostate cancer specialist at Washington University School of Medicine in St. Louis and a spokesperson for the American Society of Clinical Oncology. He was not involved with the work.

What is really exciting, Roth tells WebMD, is the prospect that the once-a-day treatment might be able to be used earlier in the course of disease, thereby delaying the time until men need chemotherapy. That is being tested in a large study now.

Also at the news briefing, researchers reported that an experimental radiation-emitting agent that targets bone both extended survival and delayed cancer-related bone problems in men with late-stage spreading prostate cancer.

The intravenous drug, known as Alpharadin, is undergoing FDA review. Roth says that since MDV3100 and Alpharadin work in different ways, they might work well in combination. No price has been set for either drug.

These findings were presented at a medical conference. They should be considered preliminary as they have not yet undergone the "peer review" process, in which outside experts scrutinize the data prior to publication in a medical journal.